1. Field of the Invention
The present invention relates to a semiconductor package, and more particularly, to a power module package having improved heat dissipating capability.
2. Description of the Related Art
In general, in semiconductor packages, one or more semiconductor chips is or are mounted on a chip pad in a lead frame, encapsulated with an epoxy molding compound (EMC) to protect internal parts, and mounted on a printed circuit board (PCB).
However, as high speed, large scale and highly integrated electronic devices have been rapidly developed in recent times, techniques that allow for low cost, miniaturization, and lightweight manufacturing are also required for power devices which are applied to automobiles, industrial equipment and household electrical appliances. Further, the power devices require high reliability and good temperature characteristics. Thus, a power module package for mounting a plurality of semiconductor chips on a semiconductor package is commonly used.
FIG. 1 is a sectional view of a conventional power module package, which is disclosed in U.S. Pat. No. 5,703,399, published on May 15, 1996, titled “Semiconductor Power Module”.
Referring to FIG. 1, the power module package has a structure in which a plurality of semiconductor chips, including a power circuit 9 and a control circuit 8, are mounted on a lead frame 3. In the drawing, reference numerals 1, 2, and 4a denote a heat sink, an epoxy molding compound (EMC) having a high heat conductivity, and a power circuit chip, respectively. Also, reference numerals 5a, 5b, 6a, 6b, and 7 denote a control circuit chip, a resistance component, an aluminum wire, a gold wire, and an insulating EMC, respectively.
In the power module package having the above structure, the EMC 2 having high heat conductivity is used such that the heat sink 1 which is made of copper is slightly spaced apart from the lead frame 3. Thus, the EMC 2 and the heat sink 1 dissipate heat, which is generated in the power circuit chip 4a, to the outside of the power module package. However, the above-mentioned prior art has the following problems.
First, the EMC 2 is filled between the backside of the lead frame 3 and the heat sink 1 made of copper in order to maintain insulation properties, and thus there is a limitation in completely dissipating heat generated in the power circuit chip 4a, to the outside of the power module package. Second, two EMCs having different characteristics are used in one power module package, and thus a process of manufacturing the power module package becomes complicated and it is difficult to perform the process of manufacturing the power module package automatically. Third, the heat sink 1 made of copper is used in the power module package, and a process of manufacturing the power module package is complicated, and thus a manufacturing cost is increased.